Stressor interactions in freshwater habitats: Effects of cold water exposure and food limitation on early‐life growth and upper thermal tolerance in white sturgeon, Acipenser transmontanus

Abstract

Limited food availability and altered thermal regimes (e.g. cold water releases from dams) are two common stressors threatening the persistence of fishes inhabiting anthropogenically disturbed freshwater systems. Yet, the combined effects of these stressors remain poorly characterised. To remedy this, we examined the isolated and combined effects of low temperature exposure and food restriction on specific growth rate (SGR, % body mass/day) and upper thermal tolerance (critical thermal maxima, CTMax) in larval white sturgeon (Acipenser transmontanus [Acipenseridae], 32 days post‐hatch, body mass: 0.25 ± 0.03 g, mean ± standard deviation). A 2 × 2 factorial design was implemented with fish exposed to one of two ecologically‐relevant acclimation temperatures (cold exposure: 11°C or a control temperature: 18°C) and one of two food restriction treatments designed to emulate observed declines in food availability (100% or 40% optimal feed rate) for 6 weeks (N: 3 replicate tanks/treatment, 50 fish/tank). Specific growth rate was affected by both low temperature exposure and food restriction in isolation; low temperature exposure reduced SGR by 56.5% and food restriction reduced SGR by 30.6%. Simultaneous exposure to low temperature and food restriction resulted in a greater but less than additive reduction in SGR (80.6%), indicating that the stressors interacted antagonistically. Critical thermal maxima were c. 2°C higher in 18°C‐acclimated fish (CTMax = 30.7 ± 0.4°C, mean ± standard error) compared to 11°C‐acclimated fish (CTMax = 28.6 ± 0.2°C, mean ± standard error); however, CTMax was independent of food restriction in both 11°C‐ and 18°C‐acclimated fish. These data highlight the unpredictability of stressor interactions and may guide holistic conservation strategies, which target co‐occurring stressors in freshwater habitats.

Biotic influences on drift behaviour of larval white sturgeon (Acipenser transmontanus)

“…The initiation timing of feeding was chosen to coincide with developmental milestones that may influence drift: olfactory development and initiation of exogenous feeding for larvae that develop at 14 • C (Dettlaff et al, 1993;Jay et al, 2020). Food rations were calculated using methods described in Rodgers et al (2018). Deng et al (2003) determined the optimal feeding rate for first-feeding larval white sturgeon is 26% body weight/day at 19.5 • C. Using the relationship between temperature and optimal feeding rate found by Cui and Hung (1995) for juvenile white sturgeon, optimal feeding rate decreases 54% between 19.5 and 14 were fed a commercial diet of frozen, enriched Artemia metanauplii (Hikari Bio-Pure).…”

The ecological relevance of critical thermal maxima methodology for fishes

“…A meta-analysis by Bell et al (2009) found that several behavioural traits that were repeatable often differed among age classes, across sexes (also reported in O' Donnell et al 2020) and between field and laboratory studies. Many factors can elicit plasticity (variation) in CT max estimates, including differences in life stages (e.g., Illing et al, 2020;Recsetar et al, 2012), diet (Isaza et al, 2019), water quality (e.g., Ern et al, 2016;Potts, 2020;Sardella et al, 2008), habitat (Rodgers et al, 2019), reproductive stage (Auer et al, 2021;Dahlke et al 2020;Johnson, 1976;Wheeler et al, 2022) and social status (Gilmour & Bard, 2022;LeBlanc et al, 2011). Chronic stress in fish can also impair responses to thermal stress (e.g., Gilmour & Bard, 2022;Claireaux et al, 2013;LeBlanc et al, 2011).…”

“…2020) and between field and laboratory studies. Many factors can elicit plasticity (variation) in CT max estimates, including differences in life stages ( e.g ., Illing et al ., 2020; Recsetar et al ., 2012), diet (Isaza et al ., 2019), water quality ( e.g ., Ern et al ., 2016; Potts, 2020; Sardella et al ., 2008), habitat (Rodgers et al ., 2019), reproductive stage (Auer et al ., 2021; Dahlke et al . 2020; Johnson, 1976; Wheeler et al ., 2022) and social status (Gilmour & Bard, 2022; LeBlanc et al ., 2011).…”

Cold-water pollution impacts on two ‘warm-water’ riverine fish: interactions of dam size and life-history requirements

“…For example, altered temperature regimes greatly increased mortality of larval and early juvenile life stages of razorback sucker, Xyrauchen texanus, flannelmouth sucker, Catostomus latipinnis, Humpback Chub, Gila cypha, and Colorado squawfish (pikeminnow), Ptychocheilus lucius (Clarkson and Childs 2000). Hence, changes to water temperatures are often a major stressor to riverine ecosystems and their biota (Dudgeon et al 2006;Rodgers et al 2019).…”